1. Field of the Invention
The present invention relates to the production of aluminum oxide of very high purity, of the order of 99.999% pure or higher. One use for this material is as feed material to molten baths of aluminum oxide from which large single crystals of aluminum oxide may be grown. These crystals may be cut into slices for use as substrates for the support of circuit elements in the manufacture of integrated circuits in the electronic arts. Antifriction bearings may also be made from such crystals.
2. Description of the Prior Art
In my prior U.S. Pat. Nos. 3,085,871, 2 and 3 I have disclosed a method and apparatus for producing refractory metals such as titanium by reduction, with the aid of a reducing agent such as liquid sodium, of liquid or gaseous halides of those metals in an atmosphere maintained at supra-atmospheric pressure and rich in gas of the halide of the metal to be reduced, rich in gas of the reducing agent, rich in an inert gas, or rich in a combination of such gases. The present invention, in contrast, provides a process of oxidation instead of reduction and is carried out at or near atmospheric pressure, and provides apparatus with which that process may be carried out and the oxide product thereof satisfactorily recovered.